Electrical dust precipitator utilizing liquid sprays



Sept. 5, 1944. G. w. PENNEY ELECTRICAL DUST PREGIPITATOR UTILIZINGLIQUID-SPRAYS Filed May 13, 1941 INVENTOR @/a /f /z e/vflj ATTORNEYWITNESSES:

Patented Sept. 5, 1944 ELECTRICAL DUST PRECIPITATOR UTILIZ- ING LIQUIDSPRAYS Gaylord W. Penney, Wilkinsburg, Pa., asslgnor ,to

Westinghouse Electric 3; Manufacturing Lompany, East Pittsburgh, Pa., acorporation of Pennsylvania Application May 13, 1941, Serial No. 393,190

12 Claims.

My invention relates to electrical gas-cleaning precipitators or similarapparatus for removing dust or dust-particles from gaseous streams, by

dust or dust-particles meaning any discrete foreign particulate mattercapable of being removed from a gas by electrical means and methods.

In my copending application Serial No. 393,189, filed concurrentlyherewith and entitled Electrilied liquid-spray dust-precipitator," Idisclose systems for cleaning a dust-laden gas stream by electricallycharging the dust-particles in the gas and then mixing the gas and thecharged dust particles therein with a liquid-spray having itsspray-drops charged with a polarity opposite to that on the chargeddust-particles. In the systems disclosed in the aforesaid application,the

dust-particles are charged by passing the dustladen gas through asuitable electrostatic field, and the liquid-spray is charged throughthe action of a substantially non-ionized electrostatic field having ahigh field concentration at the spray-nozzle or other spray-means forproducing the spray, the spray-charging field being produced byutilizing the spray-means as one electrodemeans and a relativelyinsulated loop or loops about the spray-means as a second oppositelycharged electrode-means, the spray-means and the loop or loops being inthe gas-conduit and the spray-drops taking a charge of the polarity ofthe spray-means. In the spray region, which is the region in which thegas and the charged dust-particles therein are mixed with the oppositelycharged liquid spray-drops, dust-particles apparently are transferred tothe spray-liquid, for by subsequently separating the spray-liquid fromthe gas, the dust-particles have been found to be in the spray-liquid.

The primary object of the present invention is to provide other systems,operating generally in accordance with the principles and teachings ofthe systems disclosed in my aforesaid application, which will have manyof the advantage; disclosed in the aforesaid application, but whichutilize somewhat different but desirable features and arrangements andwhich it was considered desirable to disclose in a separate application.

One of the objects of the present invention is to provide a means forelectrifying or charging the liquid-spray, which means will adequatelyand completely charge the spray-drops.

It is another object of this invention to provide a gas-treatingprecipitator of the type described in which the spray-drops are chargedby passing the spray through an ionizing electrostatic held, by ionizingelectrostatic field meaning a field which spatially contains chargedmatter, such as electrons, ions, or charged molecules, or combinationsthereof, and, consequently, includes a spatially ionized region.

It is another object of my invention to provide a gas-cleaning apparatusof the type described in which the spray-drops are charged through theaction of an ionizing electrostatic field of a polarity opposite to thatof the electrostatic field utilized to charge the dust-particles, butthe spray charging ionizing field being so confined or arranged thatoppositely charged dustparticles in the gas stream do not have theircharges neutralized by the spray-charging field before they can mix withthe charged spraydrops.

It is an important object of my invention to provide a charged spray inthe path of the gas carrying charged dust-particles, which spray willpresent a substantial curtain of some depth completely across thegas-stream so that the charged spray-drops and the chargeddust-particles will have an adequate opportunity to react to the endthat the gas is cleaned, whereby an increased gas flow velocity can beutilized.

In one form of my invention, a dust-precipitator means is disposed inthe gas-conduit after the dust-charging zone, and comprises anondischarging electrode-means which cooperates with an ionizingelectrode-means to produce an ionizing electrostatic field through whichthe spray flows so that the spray-drops are charged with a polaritywhich is the same'as that of the ionizing electrode-means. Thenon-discharging electrode-means takes the form, in this embodiment, of aconducting shield around the spray nozzle which can, if desired, also bepa t of the non-discharging electrode-means; and the ioniz-- ingelectrode-means takes the form of a discharging or ionizing pointed rod.

The polarity of the ionizing point of the rod is of opposite sign tothat of the ionizing electrode-means of the dust-charging field; andsince the ionizing point and non-discharging electrodemeans and nozzleassociated therewith are in the gas-stream, producing an ionizingelectrostatic field of charged matter predominately opposite in sign tothe field charging the dust-particles, it is desirable to prevent thneutralization of some or all of the charge on the dust-particles beforethey mix with the oppositely charged spray-drops. To this end a battlemeans can be provided diverting the gas-stream from the spray-chargingfield, but the non-discharging electrode-means for the spray-chargingfield can readily be adapted to this purpose so that thiselectrode-means may also act as such a battle-means. For this doublepurpose of the non-discharging electrode-means, the conducting shield ismade in the shape of an umbrella which partially encompasses theassociated discharging point or points of the spraycharging ionizingmeans, but is spaced from the discharging point or points and relativelyinsulated with respect thereto. By this expedient, the spray drops canbe charged by a spray-charging ionizing electrostatic field enveloped bythe gas-stream, but the charged dust-particles in the gas-stream mixwith the charged spray-drops outside of the main portion of thespray-charging ionizing electrostatic field and without the risl; ofcharged dust-particles being partially or completely neutralized solelyby the action of the spray-charging spatially ionized electrostaticfield.

However, the gas-flow may be somewhat disturbed because theelectrode-means for the spray-charging ionizing electrostatic field arein the gas-conduit. Consequently, in other forms of my invention, theionizing electrode-means and the non-discharging electrode-means forcreating the spray-charging ionizing electrostatic field are notdisposed in the main gas-conduit, thereby eliminating obstacles orresistance to the gas-flow.

The particular liquid used as the dust-removing spray is subject to widechoice. Economical reasons and operating considerations indicate thatordinary tap-water can be used for the spray-liquid with high cleaningefficiency, and such a liquid is especially desirable for cleaning airto be breathed. In some instances the liquid may be treated in order toimprove its wetting properties or even its hygroscopic action, as moreparticularly described in my aforesaid application. Ordinary oils, whichare insulating,can,be used for spray-liquids for precipitators embodyingmy invention, and have the advantage of being viscous so thatdust-particles will readily stick. to the spray-drops. However, an oilshould not be used as a spray liquid if such use is accompanied by anexplosive hazard, such as would be the case under certain conditionsinvolving an oil mist or spray in the presence of oxidizing gases.

Other features, objects, mod.fications and innovations of my invention,in addition to those specifically recited herein and in my aforesaidapplication, will be apparent from the accompanying drawing-which shows,more or less diagrammatically, the essential novel elements of theinstant embodiments of my invention.

In the drawing:

Figure 1 is a vertical sectional view to a part of a, gas-conduit meansincorporating one form of my gas-cleaning system?" Fig. 2 is a verticalsectional view of part of a gas-conduit means incorporating another formof my invention; and

Figs. 3 and 4 are vertical sectional views of further embodiments of myinvention.

In general my invention is adapted to be associated with, or to include,any suitable gasconduit means which provides or defines a gasflow pathfor a gas-stream; and in Fig. l the precipitator comprises part, or all,of a gasconduit means, indicated in its entirety by the referencenumeral 2, the direction of 'gas-fiow therethrough being in thedirection of the arrows shown in'the embodiments herein described. Thegas-conduits are assumed to be of vention is not necessarily limitedthereto and can be used, with suitable adaptations, to gasconduits ofcircular or other forms.

The precipitating apparatus comprises a dustcharging zone i in which thedust-particles in the dust-laden gas are charged, and a precipitatingzone 5 on the downstream side of the dust-charging zone.

The dust-charging means includes an ionizing-means comprising aplurality of relatively insulated discharging and non-dischargingelectrode-means extending transversely across the gas-conduit 2 at thedust-charging zone, and

1 may take the form of the ionizing means disrelatively rectangularcross-section but my inclosed in the E. H. R. Pegg Patent No. 2,215,298issued September 17, 1940. The discharging electrode-means comprises oneor more insulatedly supported ionizing-wires 6 each of which is spacedfrom and between a pair of tubular, ground electrodes Z3 which aregrounded, the gas-conduit 2 being also grounded, as indicated at id.

The precipitating means comprises a spraymeans and spray-charging meansfor producing a liquid-spray and charging the spray-drops of the spray.However, these operations may be performed simultaneously by acooperating relationship of the elements comprising the spraymeans andthe spray-charging means so that the two functions of producing thespray and charging the sprayedrops can be performed by one or moresingle means. The spray-means comprises a liquid supply-pipe l2 havingone or more spray-nozzles l6 through which liquid flowing through thesupply-pipe lfiis'discharged in the form of a spray in such manner thatthe spray ultimately occupies or spreads across the full transversearea. of the gas-conduit 2. Each spray-nozzle IQ is surrounded by, andin direct contact with, a non-discharging electrode-means in the form ofa shield l5 which has an umbrella shape and encompasses a dischargingelectrodemeans in the form of metallic pin or rod it or the like,terminating in a sharp point 28 spaced from and substantiallysymmetrically spaced with respect to the associated shield l6.

The rods l8 are supported on a metal rod 22 carried on an insulator 26so that the discharging electrode structure is insulated from thegas-conduit 2 and the shields 55 which are preferably of metal andconductively connected to the spray-nozzles i l of the supply-pipe 52,both of which are also of metal and grounded to the gas-conduit 2. 0 Aninsulated conductor 26 is connected to the ionizing wires 6, and aninsulated conductor 28 is connected to the supporting rod 22.

' The precipitating zone further comprises suitable expedients forseparating the spray-liquid from the gas-stream after the chargeddust-particles and the oppositely charged spray-drops have had asuitable opportunity to react to cause the dust-particles to follow thespray-liquid. Charged spray-drops will be collected on the metallicwalls of the gas-conduit 2 and also on a plurality of grounded spacedelectrodes 30 extending across the gas-conduit 2. Spray-liquid ingbottom member 48 below the gas entrance of the gas-outlet pipe 32 may besloped to the spout 34.

A suitable unidirectional source of electrical energy may be used toenergize the ionizing electrode-means of the dust-charging zone 4 and ofthe precipitating zone 5, and this is indicated. by the plus sign to theconductor 26 and they minus sign' to the conductor 28. The ionizingwires 8 can be made positive with respect to the gas-conduit 2 and theionizing points can be made negative with respect to the gas-conduit 2by grounding an intermediate point of the voltage supply. 'Many suitableconnections can be used, and I have shown a simple expedient foroppositely charging the ionizing means of the dust-charging zone 4 andof the precipitating zone 5, which comprises a voltage-divider resistor42 across the conductors 26 and 28, having an intermediate point 44grounded at "I,

.and which is preferably at the midpoint of the resistor 42. 1

The dust-laden gas-stream first passes through the dust-charging zone 4wherein the dust-particles in the gas are positively charged. Thespray-drops from the spraymozzle l4 are charged in the ionizingelectrostatic field established between each ionizing point 20 andassociated shield It so that the spray-drops will be charged negatively.However, the charged dust-particles are diverted or deflected from thefield between the ionizing points 20 and shields l6 because of theaction of the shields as gas-flow baflies. In the spray-region on thedownstream side of spray-charging field, the-spray spreads across thegas-conduit 2 so that the gas mingles or mixes with the spray and thecharged dustparticles in the gas react with the oppositely chargedspray-drops and apparently attach themselves thereto. the dust-ladenspray-liquid from the cleaned gas-stream by the means described providescleaned gas in the gas-outlet pipe 32. The grounded plates 30 whichcollect part of the spray-drops so that spray-liquid flows down-.

wardly thereon, also limits the space-charge in the spray-region. a

In the embodiments shown'in Figs. 2, 3 and 4, the spray-means andspray-charging means are disposed at one side of the gas-flow path so asnot to interfere with the flow of the gasstream. These embodiments alsodiffer from the embodiment shown in Fig. 1 in that a different ionizingmeans is provided for charging the spray-drops.

In the embodiment shown in Fig. 2 a gas-conduit 60, which is grounded asindicated at 52, has a somewhat angular shape and is provided with aclosed spray-chamber 54 at one side of the gas-conduit near a bend inthe gas-conduit ill.

the dust-charging zone 4 oi the embodiment shown in Fig. 1, is disposedin the gas-conduit- A dust-charging zone 56, similar to Subsequentseparation of ing-wires of the former are so energized that they are ata polarity opposite to that of the ionizing-wires of the latter. In Fig.2 the ionizing-wires of the dust-charging zone 4 are energized to benegatively charged, and the ionizingwires of the spray-charging zone areenergized to be positively charged, but the charging effects of thedust-charging ionizing electrostatic field and the spray-chargingionizing electrostatic field in this embodiment, as are the otherembodiments herein described, may be reversed.

The spray is established and charged outside of the main gas-stream andis introduced across the gas-stream in the region below the bend in thegas-conduit 50 so that a substantial curtain of some depth is introducedacross the gas-stream at an angle to its general direction of movement.Suitable means for decreasing the space-charge in the spray-region andfor separating the spray-liquid from the gasstream after the chargeddust-particles have mixed with the oppositely charged spray-drops can beprovided and, may follow the means shown in Fig. 1.

Fig. 3 is similiar to the embodiment shown in Fig. 2 except that thecharged spray is projected substantially perpendicularly across thegas-stream in the gas-conduit 10, for mixing with the gas-stream afterthe latter has passed through the dust-charging zone 12. Fig. 4 shows afurther embodiment in which the gas-conduit I6 is provided with analmostright-angular bend so that the charged spray is introduced into thegas-streamwith the general direction of movement of the spraysubstantially parallel to the general direction of movement of thegasstream in the downstream leg 18 of the gasconduit 16.

While I have described my invention in certain preferred embodimentsthereof, it is obvious that many modifications might be made thereto,and equivalent constructions provided.

I claim as my invention:

l. Continuously operable electrostatic precipi-' tating means forcontinuously removing foreign particles from a gas-stream and from theduct through which said gas-stream is flowing, com- "trode, saidspray-charging electrodes being spaced from each other, and means formaintaining a unidirectional potential-difierence between saidelectrodes for producing a spacial ionizing electrostatic fieldtherebetween for charging the spray-drops to a potential opposite tothat of said ionized foreign particles in the gas-stream; both thespray, as it first leaves said spray-discharge means, and thespray-charging ionizing electrostatic fleld being out of the maingas-stream path, but the spray being so directed that it i'irstpalleathrough said spray-charging ionizing electrostatic field and thenextends across the gas-stream carryingsaid ionized foreign particles;and spraysprayed liquid from the commingled liquid-spray and gas-stream,and withdrawing said liquid from the gas-stream duct.

2. The invention as defined in claim 1, characterized by saidspray-discharge means and said discharging electrode being. in aspraychamber at a side of the gas-flow path in said duct.

3. The invention as defined in claim 1, characterized by saidspray-discharge means being in the path of the gas-stream carrying saidionized foreign particles but being provided with a shield for causingthe main body of said gas-stream to bypass said spray-discharge meansand its spraycharging ionizing electrostatic field.

4. The invention as defined in claim 1,- characterized by saidspray-discharge means being inthe path of the gas-stream carrying saidionized foreign particles, and the non-discharging electrode of itsspray-charging means being in the form of a shield for causing the mainbody of said gas-stream to bypass said spray-discharge means and itsspray-charging ionizing electrostatic field.

5. Liquid-spray apparatus for causing a charged liquid-spray to bedistributed across the path of a gas-stream, said liquid-spray apparatuscomprising a pipe-means, one or more spray-discharge means associatedwith said pipe-means for delivering a liquid-spray, one or morespraycharging means comprising a discharging elec trode and acooperating non-discharging electrode, said electrodes being spaced fromeach other, and means for maintaining a unidirectionalpotential-difference between said electrodes for producing an ionizingelectrostatic field therebetween for charging the spray-drops, saidnondischarging electrode being in the form of a shield for causing themain body'of the gasstream to bypass said spray-discharge means and itsspray-charging ionizing electrostatic field.

6. Continuously operable electrostatic precipitating-means forcontinuously removing foreign particles from a gas-stream and from theduct through which said gas-stream is flowing, comprising thecombination, with said gas-stream duct, of ionizing-apparatus forionizing foreign particles in said gas-stream, whereby said foreignparticles are ionized with a predetermined potene tial-polarity;liquid-spray apparatus for causing a charged liquid-spray to bedistributed across the path of the gas-stream carrying foreign particles ionized by said ionizing apparatus, said liquid-spray apparatuscomprising spray-dis charge means for delivering a liquid-spray, one ormore spray-charging means comprising a discharging electrode and acooperating non-dis charging electrode, said electrodes being spacedfrom each other, and means for maintaining a unidirectionalpotential-difference between said electrodes for producing an ionizingelectrostatic field therebetween for charging the spraydrops with apotential-polarity opposite to that of the said ionized foreignparticles in the gasstream; both the spray, as it first leaves saidspray-discharge means, and the spray-charging ionizing electrostaticfield being out of the main gas-stream path, but the spray being sodirected that it first passes through said spray-charging ionizingelectrostatic field and then extends across the gas-stream carrying saidionized foreign particles; and spray-separation means for separatingdust-carrying sprayed-liquid from the commingled liquid-spray andgas-stream, and withdrawing said sprayed-liquid from the gas-streamduct.

7. The invention as defined in claim 6, characterized by saidspray-discharge means and said discharging electrode being in aspray-chamber at a side of th gas-flow path in said" duct.

8. The invention as defined in claim 6, characterized by saidspray-discharge means being in the path of the gas-stream carryingforeign particles ionized by said ionizing-apparatus but being providedwith a shield for causing the main body of the said gasstream to bypasssaid spray-discharge means and its spray-charging ionizing electrostaticfield.

9. The invention as defined in claim 6, characterized by saidspray-discharge means being in the path of the gas-stream carryingforeign particles ionized by said ionizing-apparatus, and thenon-discharging electrode of its spray-charging means being in the formof a shield for causing the main body of the said gas-stream to bypasssaid spray-discharge means and its spray-charging ionizing electrostaticfield.

10. In gas-treating apparatus, means for producing an electricallyionized spray, comprising a pipe-means, one or more nozzle-meansassociated with said pipe-means for delivering said spray, anon-discharging electrode immediately back of each nozzle-means, one ormore pointed electrodes in front of, spaced from, and pointing towards,each nozzle-means, and means for applying a unipotentialpotential-difference between said non-discharging electrode orelectrodes and said pointed electrode or electrodes for producing anionizing electrostatic field therebetween for charging the spray-drops.

11. The invention as defined in claim 1, char acterized by the saidspray-discharge means comprising a nozzle-means on the far side, withrespect to the gas-stream, of the main ionizing electrostatic fieldbetween the spray-charging electrodes, for establishing the sprayoutside of said main ionizing electrostatic field.

12. The invention as defined in claim 6, characterized by the saidspray-discharge means being on the far side, with respect to thegas-stream, of the main ionizing electrostatic field between thespray-charging electrodes, for establishing the spray outside of saidmain ionizing electrostatic field.

GAYLORD W. PENNEY.

